Decisions made by physicians and patients influenced the spending of $2.3 trillion on U.S. healthcare in 2008. Adults aged 65 and older account for the greatest use of healthcare services. As the baby boomers begin to turn 65 in 2011 the costs and use of healthcare among older adults will only increase. Thus the medical decisions made by this group of older (aged 65+) and emerging-older adults (aged 50-64) are particularly important. Past studies indicate that older adults tend to prefer a more passive role in medical decision-making as compared to younger adults. This trend may change in the near future as the baby boomers enter old age, given that they have been shown to prefer a more active role in decision-making. While many studies have looked at patient preferences for involvement in decision-making, few have sought to understand how patients perceive their role in decision-making and whether these perceptions vary by age. Patient reports of having made a shared decision are associated with important health outcomes such as decreased anxiety, better diabetes control, and increased use of preventative health services. Yet little is known about how patients and physicians perceive shared decision-making (SDM) - the very parties involved in the process. There is evidence to suggest that patients and physicians may perceive SDM differently than accepted definitions of SDM in the literature. Therefore, the aims of this study are to: (1) develop definitions of SDM from the perspectives of older adult patients, emerging-older adult patients, and primary care physicians, and (2) determine whether the occurrence of patient-defined SDM is associated with adherence to physician- recommended colorectal cancer screening among older and emerging older adults. This study will use qualitative and quantitative methods to provide a richer understanding of how older adults and primary care physicians perceive SDM, explore whether there are racial differences in patient perceptions of SDM, and determine whether the occurrence of patient-defined SDM is associated with patients receiving evidence- based physician recommended cancer screening. This greater understanding can then guide research to help physician's foster decision-making processes that meet patients'expectations while maximizing health. ! PUBLIC HEALTH RELEVANCE: As the baby boomers age, the already high costs and use of healthcare among older adults are expected to increase, making the medical decisions made by older and emerging-older adults particularly important. With evidence accumulating that shared decision-making improves health outcomes, a greater understanding of how older and emerging-older adults perceive shared decision-making is needed. A better understanding of older adults'perceptions can then guide physicians in how to engage older adults in a shared decision-making process, thereby promoting health among the nation's older adult population.